1. Field of the Invention
This invention relates to a zoom lens system with the function of preventing image shake, and particularly is suitable for a photographic zoom lens system.
2. Related Background Art
There are known a zoom lens system as disclosed in U.S. Pat. No. 5,270,857 wherein any lens unit in a zoom lens system comprised of two or more lens units is displaced in a direction perpendicular to the optical axis thereof to correct image shake, and a zoom lens system as disclosed in U.S. Pat. No. 5,040,881 wherein some lenses in a first lens unit fixed during zooming are displaced in a direction perpendicular to the optical axis thereof to correct image shake.
However, in the prior art as described above, it has been impossible to secure a back focal length sufficient for a single-lens reflex camera (SLR) and thus, it has been impossible to realize a desired great zoom ratio. Therefore, the zoom lens systems as described above are unsuitable as lenses for a compact and high-performance 35 mm photographic SLR.